Integrating role of ethylene and ABA in tomato plants adaptation to salt stress

Saline stress seriously disrupts the growth and physiology of plants, whereas phytohormones play an important role in regulating plant responses to salinity stress. The involvement of phytohormones in salt tolerance of tomato and the interaction between potassium and phytohormones was studied in relatively salt-tolerant (Indent-1) and salt-sensitive (Red Ball) genotypes under salt stress at three levels of NaCl (0, 75, 150 mM) combined with two levels of K (0, 4.5 mM) under controlled conditions in a climatic chamber. Results showed that the salt-tolerant genotype had significantly higher concentrations of ABA and ethylene under saline conditions compared to control (0 mM NaCl) and salt-sensitive genotype. The concentration of hormones was significantly higher in the treatment where no K was applied and it was lower in treatments where K was applied indicating that K application reduced the negative impact of salinity stress and thus increased the hormone concentration. Enhanced concentration of hormones in salt-tolerant genotype positively affected plant physiology and thus better chlorophyll content index (CCI), stomatal conductance and ion homeostasis that is higher K+/Na+ ratio in the xylem. Salt stress altered the stomatal morphology and significantly decreased stomatal density and aperture in both genotypes. It was concluded that under salt stress enhanced phytohormones concentration positively affected the tomato plant physiology, especially in the salt-tolerant genotype and this could be one of the factors responsible for its better salt tolerance. Potassium application served as ameliorant and reduced the negative effects of salt stress and could be used as an effective tool for tomato production. (C) 2014 Elsevier B.V. All rights reserved.